1. Field of the Invention
The present invention relates to a transparent card with a hologram, having the excellent design property and a high security property.
2. Description of the Related Art
The hologram is produced by having two lights of the same wavelength (object light and reference light) interfere with each other so as to have the wave surface of the object light recorded on a sensitive material as interference fringes. If a light of the same condition as the original reference light is directed to the hologram, the diffraction phenomenon is generated by the interference fringes so that the same wave surface as the original object light can be reproduced. The hologram can be classified into several kinds (surface relief type hologram, volume type hologram, or the like) according to the recording form of the interference fringes generated by the interference of a laser beam or a light of the excellent coherence property.
Since the hologram has the advantages such as the beautiful external appearance and the difficulty in copying the same design, it is used frequently for the security application, or the like. In particular, as to the plastic cards represented by the credit cards, the cash cards or the like, a card with a hologram is broadly used mainly from the viewpoint of the copy prevention and the design property contribution. As the hologram used for the cards with a hologram, a surface-relief reflection type hologram with the interference fringes recorded by applying a minute concavo-convex shape on the hologram formed layer surface is commonly used.
However, recently, it is pointed out that the relief type hologram can be copied easily so that deterioration of the copy prevention function by applying a hologram on a plastic card is regarded problematic. Moreover, according to a transparent card referred to as a skeleton card disclosed in the Japanese Patent Application Laid-Open (JP-A) No. 2005-103957, deterioration of the design property derived from the transparency in the case of applying the conventional reflection type hologram has been pointed out, and thus incapability of utilizing the advantage of the transparent card with the excellent design is regarded problematic.